Greece Is Showing 'Reform Fatigue': IMF Chief Lagarde

French Finance Minister Christine Lagarde is considered the top contender to replace Strauss-Kahn as IMF chief.

France, Germany, and other euro zone countries want Greece to remain in the monetary union, "but there will be a price," Christine Lagarde, managing director of the International Monetary Fund (IMF), told CNBC Thursday.

Greece is making progress on reforms but needs to do more if it wants to get additional financing from European Union members or the IMF , she said.

"It's a question of keeping at it," she noted, adding that after last year's 5 percent deficit reduction, Greece has shown "reform fatigue" and the pace of making changes has slowed.

She applauded Wednesday's statement by German Chancellor Angela Merkel and French President Nikolas Sarkozythat "provided a country in the program, such as Greece, performs its obligations, the euro members will financially support it," Lagarde said.

"The IMF operates in the same fashion in all its programs. We look at the commitments…we see whether there has been implementation and release the financing tranche," she said. If there has been no implementation, there will be no financing, Lagarde said.